Sear device for a firearm



E. C. LEE

SEAR DEVICE FOR A FIREARM Oct. 21; 1958 Filed Nov. '25. 1953 3 Sheets-Sheet 1 INVENTOR. E dwn'rcl [L L E E ad/paw A TTGR N E; s

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SEAR DEVICE FOR A FIREARM Filed NOV. 25, 1953 3 Sheets-Sheet 2 IN V EN TQR.

Edward E..-Lee

m: *amw A TTOR/VEYS Oct. 21, 1958 E. c. LEE

SEAR DEVICE FOR A FIREARM 3 Sheets-Sheet 3 Filed NOV. 25, 1953 IILIIM uvmvron E dwurd ELLE E I m I ATTORNEYS engagement with the sear.

United States Patent SEAR DEVICE FOR A FIREARM Edward C. Lee, Detroit, Mich., asslgnor to the United States of America as represented by the Secretary of the Army Application November 25, 1953, Serial No. 394,523

' 1 Claim. (Cl. 89-136) This invention relates to automatic firearms wherein a firing member is resiliently mounted for slidable movement in a reciprocating bolt and is particularly directed to means for securing the firing member in a cocked position and for the release thereof when the bolt is in a battery position.

In automatic firearms of the type described in Patent No. 1,628,226 to John M. Browning, there is provided a longitudinally reciprocating bolt having a spring-biased firing member mounted for slidable movement between a forward firing position and a rearward cocked position. The firing member is arranged to be releasably retained in the cocked position by a spring-biased sear mounted for reciprocal movement in vertical slideways. When the bolt is moved to the battery position, the sear is actuated by suitable means to release the firing member which moves forwardly under the bias of its spring to discharge the chambered cartridge. During the ensuing recoil movement of the bolt, a cocking lever pivotally mounted therein, moves the firing member rearwardly ready for During counterrecoil of the bolt, the cocking lever is counter-rotated permitting the firing member to be biased slightly forward into releasable engagement with the scar, and the bottom end of such cocking lever is swung free of the firing member whereupon the latter is free to move forwardly when released by the sear to effect another cycle of operation.

In firing mechanisms of this type, considerable trouble has been experienced with the sear prematurely releasing thefiring member whereby the chambered cartridge is not ignited because of the lack of a proper blow by the firing member on the primer.

Accordingly, it is an object of this invention to provide in an automatic firearm, a cylindrical vertically reciprocating sear which moves smoothly between holding and disengaged positions and has positive engagement with a firing member.

It is a further object of this invention to provide in an automatic firearm, a sliding cross member which both locks the sear in engagement with the firing member and actuates such sear.

It is the specific object of this invention to provide for an automatic firearm bolt, a cylindrical vertically sliding sear which may be actuated from both the right hand and left hand side of the belt or the top thereof and an actuating cross member to releasably lock the sear in engagement with the firing member.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawing in which:

Fig. l is a longitudinal cross-sectional view of a firearm bolt showing the firing member in retracted position;

Fig. 2 is a fragmentary view similar to Fig. 1 but showing the firing member in firing position;

Fig. 3 is a partially cross-sectioned end view of the bolt showing the cross member installed therein for actuation from the left side of the bolt;

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Fig. 4 is an enlarged exploded view of the sear and firing member mechanism;

Fig. 5 is an end view of the bolt partially cross-sectioned to show the sear in locked holding position and the cross member installed for actuation from the right side and the top of the bolt;

Fig. 6 is a view similar to Fig. 5 but showing the sear partially unlocked bythe actuator member and the sear engaged thereby; and

Fig. 7 is a view similar to Figs. 5 and 6 and showing the sear fully depressed by the actuator member.

Shown in the figures is a bolt 12 of the well-known Browning type in which there is mounted afiring member 13 reciprocable between a retracted and a firing position, a cylindrical sear 14 for holding such firing member in a cocked position and a rectangular cross member 15 which both releasably secures such sear in engagement with the firing member and actuates the sear to a disengaged position. Provided in bolt 12 is a longitudinal well 16 and a bore 17 of smaller diameter which extends axially forward from the end thereof to form an annular shoulder 18. A vertically disposed cylindrical hole 19 is arranged to intersect well 16 and is terminated by an end wall 42. A cylindrical slideway 20 having oppositely disposed rectangular channel portions 21 extending vertically therefrom traverses hole 19 laterally above well 16. Provided in the top side of bolt 12 is a recess 22 which communicates rearwardly withhole 19. A vertical slot 23 and a bore 24, disposed forwardly therefrom, extend downwardly from the bottom side of recess 22 to communicate with well 16. Mounted in recess 22 is a member 25 comprised of a pin portion 26, which is receivable by bore 24 and arranged to extend into well 16, and an arm portion 27. The front end of arm portion 27 is terminated by an upwardly arching arcuate portion 28 and the rear end is arranged to be normally contiguous one side of slot 23.

Firing member 13 is comprised of a striker portion 29, slidably receivable in bore 17, and an extension portion 30, slidably receivable in well 16. The junction of striker 29 and extension 30 forms an annular ledge 31 which is engageable with shoulder 18 to establish the firing position of firing member 13. Provided in extension 30 is a longitudinal hole 32, which receives a compressible spring 33, and a rearwardly adjoining vertical slot 34 which receives pin portion 26 of member 25 so as to engage the end of spring 33 whereby firing member 13 is biased to the firing position.

Provided in the underside of the rear portion of firing member 13 is a slabbed portion 38 and depending downwardly from the rear end thereof is a forwardly facing hook 39. A tongue portion 40 projects rearwardly from the end of extension 30, with the underside thereof planarily aligned with the underside of hook 39, and a lug 41 extends upwardly from such end.

A cocking lever 35 is intermediately mounted in slot 23 on a transverse pin 36. The end of cocking lever 35 extending below pin 36 is receivable by slot 34 and is arranged to be engageable with the rear wall thereof. The upper end of cocking lever 35 is receivable in a V- slot 37 provided in the top plate bracket of the weapons receiver (not shown) whereby during recoil of bolt 12 such cocking lever is rotated to actuate firing member 13 against the bias of spring 33 to the retracted position. During counter-recoil of bolt 12, the top end of cocking lever 35 reengages with V-slot 37 whereby" such cocking lever is counter-rotated permitting firing member 13 to be biased by spring 33 slightly forwardto be engaged by sear 14, as hereinafter described, with the bottom end of such cocking lever rotating free of extension 30.

Sear 14 is mounted in hole 19 for slidable movement between an upward holding position and a downward disengaged position which because of the large cylindrical between the holding and disengaged positions.

bearing surface is accomplished smoothly and without frictional chatter. Provided in the bottom portion of scar 14 is a concentric hollow receptacle 63 which receives one end of a coiled spring 43. The opposite end of spring 43 bears against wall 42 of hole 19 whereby sear 14 is biased to the holding position. A recess 44, similar in conformation to the rear end of firing member 13, is provided in sear 14. Recess 44 is arranged to receive the rear end of firing member 13 when in the retracted position and at the same time permit movement of scar 14 Provided in the bottom side of recess 44 is an indent 48 which forms a rearwardly facing lip portion 45 cooper-able with book 39 for releasably latching firing member 13 in cocked position. The bottom sides of hook 39 and tongue 40 are arranged for slidable engagement with the top side of lip 45 when firing member 13 moves between cocked and fired positions and thereby holds sear 14 in a disengaged position. A groove 47 extends vertically downward from indent 48 and is arranged to slidably receive the end of tongue 40 during installation of scar 14 in cylinder 19. When lip 45 is depressed past tongue 40 during such installation, sear 14 is turned 90 until lip 45 is aligned for cooperation withhook 3 9. Assembly of cross member 15, which, transverses sear 14 as herein-- after described, secures sear 14 against rotation.

Provided transversely through sear 14, above recess 44,

is a rectangular channel 49 the bottom side of which is terminated at both ends by similar downwardly inclining cam surfaces 50. A rectangular groove 51 is arranged between the upper portionof recess 44, whichreceives lug 41, and channel 49. Av cylindrical hole 52 extends downwardly from the top side of sea 14 to communicate cocking lever 35 is checked by arcuate portion 28 of member 25. I 1 I 7 Cross member is arranged as hereinafter described for reversible installation through bolt 12 and sear 14, by means of rectangular portions 21 and channel 49, and for slidable movement therein. The front and rear sides of one end of cross member 15 are cut away, as noted by 54, to form a T-section portion 55 and similar terminating ledge portions 56 which are arranged to mate with cam surfaces 50. The vertical bar portion of T-section 55, noted by 57, is arranged to be slidably received by groove 51 and the ledges 56 to be engageable with either pair of cam surfaces 50 whereby a lateral force, exerted against the opposite side of cross member 15, noted by 65, causes such ledges to cooperate with the engaged cam surfaces to depress sear 14 to the disengaged position. Spaced apart from cut-away portions 54, toward end 65, are triangular cavities 64, one side of each, noted by 75, being parallel with ledges 56. A divider portion 58 is formed between cavities 64. Also provided in end 65 is an elongated slot 61 which is arranged to slidably receive to bisect cam surfaces 50 and to provide communication a pin 62 longitudinally mounted in bolt 12, whereby the lateral movement of such cross member 15 between a locking and a sear actuating position is limited.

A cup-like housing 67, having a pair of diametrically opposed holes 68 therethrough, is partially receivable in either end of slideway 20 and is secured therein by a pin 69 one end of which is receivable in one of such holes. Housing 67 is installed in slideway 20 so as to be adjacent the end of T-section 55. One end of a coiled spring 70 is receivable in housing 67 and the other end bears against the end of T-section to bias cross member 15 to the locked position.

The top side of cross member 15 is cut away to form a locking lug which is arranged to be engageable with the top side of channel 49 adjacent end when such cross member is in locked position. The engagement of locking lug 60 with the top side of channel 49 blocks sear 14 from being depressed to disengaged position and such locking lug is arranged to be receivable by hole 52 when cross member 15 is in sear actuating position and sear 14 is depressed to disengaged position.

Pins 69 and 62 are arranged to be interchangeably mounted in bolt 12.

A longitudinal slot 72 is arranged through vertical bar 57 of T-section 55 for receiving lug 41 when firing member 13 is in retracted position and thereby secures cross member 15 in locked position. When firing member 13 is released by cocking lever 35 during counter-rotation and goes forward to be engaged by sear 14, lug 41 moves forwardly oht of slot 72 tounblock cross member 15.

A rectangular channel 80 extends vertically downward from the top side of bolt 12 adjacent cylinder 19 and is arranged for one side to communicate therewith. Mounted for slidable movement in channel 80 is an actuator member 71. The bottom side of actuator 71, noted by 82, inclines downwardly so as to be mateable with cavities 64 and a lateral groove 76 extends upwardly therefrom to receive divider portion 58 as the lower end of such actuator is received by such cavities. Actuator 71 is so arranged that when a vertical force is exerted against the top side thereof, bottom side 82 cooperates with sides of cavities 64 to earn cross member 15 towards sear actuating position. When cross member 15 is moved to where locking lug 60 has unblocked sear 14, a

step'portion 77 on actuator 71 is arranged to engage the top side of such sear whereby continued downward'force on such actuator istransferred by such step directly to the top side of such sear which is depressed thereby to disengaged position. Actuator 71 is retained in bolt 12 by arm portion 27 of member 25 which is slidably received by an indent 79 provided in such actuator. Cocking lever 35 engageably maintains arm portion 27 in indent 79.

In the hereinbefore described embodiment of the sear 15 is assembled in such bolt so that cavities 64 are in position to cooperate with actuator 71 as best shown in Figs. 5, 6 and 7, or from the opposite side when such cross member is reversely mounted in such bolt, as best shown in Fig. 3. In the latter case, actuator 71 is removed from bolt 12.

When the firearm embodying the sear mechanism of this invention is fired, bolt 12 is recoiled causing cocking lever 35 to be rotated on pin 36 by the engagementof the top side thereof with V-slot 37 in the top plate bracket of the firearm receiver. The rotation of cooking lever 35 forces firing member 13 rearwardly by the engagement of the bottom side thereof with the rear end of slot 34. As firing member 13 is moved rearwardly, the bottom sides of tongue portion 40 and hook 39 move slidably along the top side of lip 45 until such hook is retracted past lip 45. When book 39 moves past lip 45, sear 14 is free to be biased upwardly by spring 43 with hook 39 moving into indent 48.

When the firearm is fired, cross member 15 is moved to sear actuating position, either by actuator 71 or directly by a trigger mechanism (not shown), and sear 14 is depressed thereby to disengaged position. Sear 14 is held depressed after the release of firing member 13 by the engagement of the top side of lip 45 with the under sides of tongue 40 and cross member 15 is held in sear actuating position by the engagement of the side of lug 60 with the adjacent top side to recess 44 until such sear moves upwardly into holding position at the return of such firing member to retracted position. When sear 14 reaches holding position, lug 60 is disengaged therefrom and cross member 15 is free to be biased by spring 70 to locked position wherein lug 60 blocks such sear from being depressed to disengaged position and slot 72 is positioned to receive lug 41 of firing member 13 when retracted. Hence, sear 14 is locked in holding position by cross member and such cross member is blocked from moving from the locked position.

Upon the ensuing. counter-recoil of bolt 12, the top of cocking lever reengages with V-slot 37 to cause counter-rotation of such cocking lever. rotation permits firing member 13 to move forwardly under the bias of spring 33 until engagement is made between hook 39 and lip 45, whereby such firing member is cocked when bolt 12 moves into battery, and lug 41 is moved out of slot 72, freeing cross member 15 for movement to sear actuating position.

When the gun is arranged to be fired from the side, cross member 15 is assembled in bolt 12 so that end 65 is engageable with a trigger mechanism (not shown) mounted on the selected side. Actuation of such trigger mechanism is arranged to move cross member 15 laterally whereby lug 60 is moved into hole 52 out of engageable position with the top side. of recess 44, thus freeing scar 14 for movement away from holding position. Continued movement of cross member 15 engages ledges 56 with the corresponding cam surfaces to cammingly depress sear 14 and thereby release firing member 13 which is biased forwardly by spring 33 to fire the chambercd cartridge.

When it is desirable to operate the firearm from the top side, actuator 71 'is assembled in channel 80 and cross member 15 is installed so that sides 75 of cavities 64 are arranged to cooperate with bottom side 82 of such actuator. Thus, when a vertical force is applied to the top side of actuator 71 bythe trigger mechanism '(not shown), sides 82 cooperate with sides 75 to cammingly move cross member 15 to sear actuating position. When cross member 15 is moved to where lug unblocks sear 14, step 77 of actuator 71-contacts the top side of sear 14 so that the force of the trigger mechanism is applied 3 directly thereto to depress such sear to disengaged position.

From the foregoing, it can readily be seen that there is here provided a sear mechanism of superior design. It

is obvious that by the sear being cylindrical in design, it 4 moves more freely in the bolt and is less susceptible to frictional chatter during reciprocation. It is further obvious that by the sear being cylindrical in design, it moves more freely in the bolt and is less susceptible to frictional chatter during reciprocation. It is further obvious that by the firing member being in continual contact with the sear, rather than making engagement therewith by impact as in'conventional designs, the sear is maintained under control. Moreover, the sear mechanism is provided with a positive meansof locking the sear in holding position and further issimple, rugged and effective in design.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope Such counter- 5 thereof and the following such variations.

Iclaim:

In a firearm bolt, a firing member mounted for reciprocable movement between a firing position and a retracted position, said firing member being provided with an upstanding lug adjacent the rear end, a tongue portion extending rearwardly therefrom and a forwardly facing hook portion, a cylindrical sear mounted in a mating hole in the bolt for slidable movement between a firing member holding position and a disengaged position, said sear being provided with a recess for receiving the rear end of said firing member including said tongue portion, said lug portion and said hook portion, a channel having a top side transversing the top portion of said recess and a coaxial bore extending from the top of said sear to said channel, oppositely inclining surfaces in said channel, a lip portion projecting upwardly from said recess, said lip being cooperable with said hook portion for releasably holding said firing member in a cocked posiclaim is intended to include tion between said firing position and said retracted position, a cross member mounted in said channel for slidable movement in response to an outside force, said cross member being provided with a cam portion selectively cooperable with said inclining surfaces whereby said sear is cammingly moved by said cross member to said disengaged position from either side of the bolt, a slot for receiving said lug on said firing member when said firing member is in said retracted position and a lock portion engageable with said top side of said channel for blocking said sear in said firing pin holding position, means for limiting movement of said cross member cooperable with said cam portion and said locking portion being so that said lock portion is out of blocking relationship with said sear when said cam portion engages the selected one of said inclining surfaces, a spring cooperating with said cross member for biasingsaid lock portion into engageable relationship with said top side of said channel, and an actuator member slidably responsive to an outside force, said actuator being provided with an angular bottom side cooperable with a sloping surface on said cross member for cammingly moving said cross member out of blocking engagement with said scar and a stepped portion engageable with the top side of said sear for direct actuation thereof to said disengaged position after said cross member is moved out of blocking engagement therewith.

References Cited in the tile of this patent UNITED. STATES PATENTS 1,677,588 Gorton July 17, 1928 1,949,418 Howard Mar. 6, 1934 1,981,855 Coupland Nov. 27, 1934 2,395,023 Swebilius Feb. 19, 1946 2,462,114 Lochhead' Feb. 22, 1949 

